Experimental investigation of partially confined concrete-filled steel tubular square columns under lateral cyclic loading

This paper presents an experimental investigation on partially confined concrete-filled steel tubular (PCCFST) square columns (i.e., short inner concrete core confinement near the support), using circular hollow section (CHS) configuration as partial inner confinement, under combined axial and cyclic lateral loadings. Hysteretic behavior of load, ultimate lateral strength, energy dissipation capacity, and ductility of the PCCFST columns were studied as a function of (a) the ratio of the height of the inner tube to the diameter of the outer tube (0-2.5) and (b) diameter/width ratio of inner tube to outer tube (0.44, 0.53). Based on the investigation, it has been seen that the height and diameter of the inner CHS have an evident influence on the cyclic performance of the column. Ultimate lateral strength, energy dissipation capacity, and ductility were enhanced by similar to 15.3%, 11.4%, and 9.6%, respectively, up to a height of 1.5D of inner CHS. Enhancement of the cyclic performance of PCCFST column with the height of inner CHS beyond 1.5D is not very significant. Based on the limited experimental results herein and code provisions (Eurocode 4), a design rule has been proposed to predict the ultimate lateral strength of the PCCFST columns.